Blind people, unable to see things with eyes like normal people do, mainly rely on the auditory sense of ears and the tactile sense of fingers to acquire external information. In order to facilitate the studying and information communication of the blind people, some documents in Chinese, English, French or other languages are usually converted to braille books for the blind people to read. The braille, also called as dot character or embossed character, is the writing specially designed for the blind people and perceived mainly by the tactile sense. Generally, each braille dot character includes 6 dots, and these 6 dots are equally divided into two groups arranged side by side. The braille books are formed by making different combinations of the braille dot characters on paper sheets by means of a braille plate, a braille typewriter or a braille printer.
With the development of informatization and popularization of personal computer, there has appeared Chinese character braille conversion software which can be installed in computers. Such software can convert the Chinese characters in a computer to braille coding. However, the personal computers generally display graphics or texts through a screen, while the blind people cannot see the braille displayed on the computer screen. The braille dot character display, shorted as dot display, also called as braille electronic display or braille typewriter, can synchronously display using braille the information in the computer for facilitating touch reading of the blind people, and through cooperation with the screen reader, can display using braille the text read by a screen reader on a display. Braille dots on the display will automatically protrude, and the blind people read the text through the tactile sense.
Currently, the braille displays in domestic and overseas markets are mainly made from piezoelectric materials, and they trigger the conversion of recessing and protruding of the braille dots by controlling changes of volumes of the piezoceramics, therefore, they are large in volume and high in cost. Besides, designing the braille display with ultrasonic wave arrays and electroactive polymer (EPA) materials is being under research in overseas laboratories, but they are too high in cost to be commercialized, and have not been publicly presented yet. A braille display developed and manufactured by Tsinghua University consists of 40 automatic braille units, and can convert the text information in the computer to the braille by a screen reader and then automatically display the braille, thus the blind people can acquire the information displayed on the computer screen by touching with hands the braille dot characters on the braille units. However, since it realizes the conversion of recessing and protruding of the braille dots by controlling changes of the volumes of the piezoceramics, it has a too big volume; besides, a new recessing-protruding dot array sensor made by Tsinghua University in cooperation with Japan is manufactured by an extremely deformable electrostrictive material, and has a high driving voltage and a complex driving circuit, therefore, the driving circuit has a big volume, and the whole product is not easy to carry, and is high in cost. On the other hand, the cost is relatively high, thus it cannot meet the conditions of common families of blind people, and currently is mostly purchased by educational establishments for blind people.